74 BIOLOGY AND TECHNIQUE 



the broth and can be transmitted in series from broth fishings of 

 irregular colonies in the same way as from dissolved cultures. 



If a number of irregular colonies are obtained on a streak plate, 

 it will be found that on examining with the microscope or often 

 with the naked eye, that there are minute transparent masses be- 

 tween the irregular colonies, which are referred to by most writers 

 as "appearances." On examining the irregular lytic colonies under 

 the microscope it will be found that the lytic colonies owe their 

 irregular shape to the fact that their edges have faded out into these 

 transparent appearances. All attempt to find a definite structure 

 in the "appearances" by different methods of staining have failed, 

 and we have no reason to believe that they are living. In our 

 opinion the "appearances" represent the debris left when the sus- 

 ceptible bacilli in any culture are dissolved by action of the lytic 

 principle. 



The two most striking facts about these lytic agents from what- 

 ever source they are derived are: (1), that a single contact with 

 the lytic agent is sufficient to divide a normal culture into two types 

 of organisms, one the resistant type, the other the bearer of the 

 lytic principle; (2), that the lytic principle could only be transmitted 

 in series when young actively growing cultures were used. This 

 suggested that once the dissolving action was started, the lytic agent 

 in subsequent generations was derived from the bacterial cell itself. 

 Experiments were consequently undertaken to isolate a lytic agent 

 which would start the dissolving process without any interaction 

 of the living animal body. 



The early work of Twort in connection with vaccine virus sug- 

 gested that tissue enzymes might be able to start the process. In 

 consequence glycerine extracts of intestinal mucosa have been made 

 and such extracts when added to young turbid typhoid or dysentery 

 cultures in a dilution of 1-10 have had a dissolving action on the 

 bacilli which is transmittible in series. Liver extracts prepared 

 according to the method of Turro 38 have given similar results. 



Bordet has recently prepared an antilytic serum. 39 In trying 

 to duplicate his experiments, and testing the normal rabbit serum 

 comparatively with the immune serum, it was found that in some 

 instances the normal rabbit serum had a dissolving action when 



88 Turro, Compt. Bend, de la Soc. Biol., February 12th, 1921. 



39 Bordet and Ciuca, Compt. Eend. de la Soc. Biol., February 5th, 1921. 



